Web density control means for web forming apparatus



June 21, 1966 R. c. DRAVlNG 3,256,569

WEB DENSITY CONTROL MEANS FOR WEB FORMING APPARATUS Filed Sept. 24, 1963 FIGI.

FIGZ.

INVENTOR: D R AV ING ROBERT C.

ATTYS nited States Patent 3,256,569 WEB DENSITY CUNTROL MEANS FOR WEB FORMING APPARATUS Robert C. Draving, Fort Washington, Pa., assignor to Proctor and Schwartz, Inc, Philadelphia, Pa., 21 corporation of Pennsylvania Filed Sept. 24, 1963, Ser. No. 311,082 1 Claim. (Cl. 19-1564) prior to delivery of the fibrous material to a carding machine, nevertheless the density of the batt presented to the feed rolls is not uniform and affects the density of the finished web.

Heretofore control of web density has been largely a sampling procedure with the feed roll speed being manually varied in response to variations in web density to compensate for such variations. Such control operations are time consuming and by nature subject to inaccuracies. In most instances there is a considerable time lag between the deviation of a web from the desired density and the changing of the feed roll speed to correct such deviation.

It is accordingly a primary object of the present iu vention to provide an arrangement for automatically and continuously maintaining a predetermined uniform web density of a fibrous web as it is formed on web forming apparatus. 4

Additional objects and advantages of the invention will be more readily apparent from the following detailed description of embodiments thereof when taken together with the accompanying drawings in which:

FIG. 1 is a schematic side elevational view showing web forming apparatus including an embodiment of the present invention for automatically maintaining a uniform web density;

*FIG. 2 is an enlarged view of the web forming area of FIG. 1 showing additional details of the web forming area; and

FIG. 3 is a view similar to FIG. 2 showing a modified embodiment of the invention.

Referring to the drawings, FIG. 1 shows a web forming machine which in this instance is a combination garnett and air doffer having a feed apron 10 for advancing fibrous material 12 into feed rolls 14 and 16. The feed rolls are driven by motor 18 through variable speed drive means 20.

The fibrous material passes through the feed rolls from which it is picked up by lickerin 22, lumper 24, and the first main cylinder 26. As the material passes around the first main cylinder the fibers are separated, straightened and leveled by workers 28, 30 and 32 and their respective strippers 3 4, 36 and 38. Passing under fancy roll 40 and fancy stripper 42, the material is transferred from the first main cylinder by doifer 44 to the second main cylinder 46 on which it is subjected to worker 48 and stripper 50. As the fibrous material reaches the top of the second main cylinder it is engaged by an air flow passing along air plate 52 and advanced against the perforate condensing cylinder 54. Vacuum box 56 within the condensing cylinder 54 causes the air flow to pass through the perforate cylinder, depositing the fibrous materials as a web 5 8 on the perforate cylinder surface. Sealing roll 66 effects the desired compacting of the web which travels over the condensing cylinder and onto delivery apron 62.

The condensing cylinder is supported and driven by drive wheels 64 and 66 and maintained in position by hold down wheels 68. The vacuum box 56is connected at the ends of the-condensing cylinder with ducts 70 leading into the fan 72. The air from the fan is directed into an air balancer 74, through curved duct 76 and along the air plate 52 into the vacuum box 56 through the perforated condensing cylinder.

By reference to FIG. 2 or 3 the air flow and fiber path in the Web forming area adjacent the condensing cylinder may be more clearly understood. The fibrous material passes from the toothed wire surface 78 of the second main cylinder 46 into the web forming area 80. The material is removed from the main cylinder by the air stream passing along the air plate 52 in conjunction with the dofi'er blade 81 positioned tangentially to the main cylinder between the main cylinder and the condensing cylinder. The fibrous material is directed as shown against the condensing cylinder 54 with the air stream passing through the holes 84 in the cylinder into the vacuum box 56 The above described apparatus of a type known in the art is typical of the type of equipment with which the present invention as described below may be employed.

The embodiment shown in FIGS. 1 and 2 includes pressure sensing means consisting of a conduit 86 opening into the web-forming area by means of threaded fitting 88 secured in the air plate 52. The conduit 86 leads into a pilot controller 90 which in response to variations of pressure in the web forming area varies the speed output of the variable speed drive means 20 by actuation of pneumatic speed varying cylinder 92 through the conduits 94 and 96. The variable speed drive means may for example be a Reeves drive or other suitable speed changing mechanism.

In operation, the embodiment shown in FIGS. 1 and 2 functions in the following manner. Should the density of the web forming on the condensing cylinder become lower than desired, the air flow along the air plate 5 2 increases in velocity due to the decreased resistance presented by the forming web. The increased air velocity along the air plate results in a decreased pressure in the conduit 86 and the pilot controller d0 translates such a pressure change into the requisite speed control for the variable speed drive means 20 so as to increase the speed of the feed rolls 14 and 16 and thus deposit a denser web upon the condensing cylinder. The main cylinders, workers and condensing cylinder are driven independently of the feed rolls and it is thus only the speed of the feed rolls which is altered to change the web density.

If, on the other hand, the density of the web in the web forming area should increase above a predetermined density limit, the air passing along the air plate is decreased in velocity due to the increased resistance of the denser web. As a result, the air pressure in the conduit 86 as sensed by the pilot controller 90 is increased and in response the controller decreases the speed of the feed rolls 14 and 16 to decrease the density of the Web formed on the condensing cylinder.

With webs of substantial width, it is desirable to employ two or more pressure sensing means spaced along the air plate such that an average pressure in the web forming area may be fed into the pressure sensing unit 90. This may be accomplished by joining the several conduits of the pressure sensing means prior to connection with the pilot controller.

In the embodiment shown in FIG. 3, an additional pressure sensing means is provided in the vacuum box 56 for sensing the negative pressure in the box and includes Patented June 21, 1966 conduit 98 connected with the vacuum box by fitting 100. The addition of such pressure sensing means in the vacuum box permits a sensing by the pilot controller 90 of the variations in the pressure differential between the air plate and the vacuum box, which pressure variations would be of a greater magnitude than those obtainable simply by sensing the pressure changes at the air plate. Accordingly, the arrangement shown in FIG. 3 would permit a substantially greater accuracy of control than the embodiment shown in FIGS. 1 and 2. As was suggested with respect to the pressure sensing means on the air plate, it is preferable to include a plurality of spaced pressure sensing means on the vacuum box to permit an averaging of the negative pressure readings.

Although in the embodiments shown a pilot controller is employed to pneumatically vary the speed of the drive means, it is obvious that other pressure sensitive arrangements could be employed such as an electric pressure gauge to activate an electric speed varying device upon deviation of the web density from pre-established density limits.

Manifestly, changes in details of construction can be effected by those skilled in the art without departing from the spirit and the scope of the invention as defined in and limited solely by the appended claims.

I claim:

In a machine for forming a continuous web of fibrous material at a constant rate including feed rolls for advancing fibrous materials into the machine, variable speed drive means for driving the feed rolls, a condensing cylinder, means for driving said condensing cylinder at a constant speed, a main cylinder closely adjacent the condensing cylinder, a restricted web forming area between the main cylinder and the condensing cylinder having a narrow portion adjacent the main cylinder and an enlarged portion adjacent the condensing cylinder, means for passing air under pressure through the restricted webforming area for dofiing fibrous material from the periphery of the main cylinder to the peripheral surface of the condensing cylinder, pressure sensing means for sensing variations in pressure in the narrow portion of the web-forming area, and controller means connected with said pressure sensing means operable for varying the speed of said feed roll drive means in response to variations in density of the fibrous web, the pressure in said web-forming area being proportional to the density of the web, whereby a predetermined uniform web density and a constant web travel rate may be continuously and automatically maintained.

References Cited by the Examiner UNITED STATES PATENTS 974,858 11/1910 Brown 19156.4 2,152,901 4/1939 Manning. 2,648,876 8/1953 Phillips et al. 19106 X 2,703,441 3/1955 Langdon et al. 19156.1 2,952,047 9/1960 Lytton et al. 3,010,161 11/1961 Duvall 19-156 3,037,248 6/1962 Callaghan 19-156.4 3,108,332 10/1963 Moss et a1. 19--204 X FOREIGN PATENTS 880,698 10/1961 Great Britain.

DONALD W. PARKER, Primary Examiner.

D. NEWTON, Assistant Examiner. 

